1. Field of the Invention
The present invention relates to a data processing apparatus and method of embedding or embedding watermark information in image data or audio data and a storage medium storing the method.
2. Related Background Art
With the recent remarkable advances in computers and networks, various types of information, e.g., character data, image data, and audio data, have been handled in networks. As for image data and audio data, relatively large amounts of data are often handled.
Conventionally, therefore, image data and audio data have been compressed to decrease the data amounts. For example, image data is compressed to transmit a large amount of image information through a network.
As the above image compression techniques, the multivalue still image compression scheme (generally called JPEG) in ITU-T recommendation T.81, the binary still image compression scheme (generally called JBIG) in ITU-T recommendation T.82, and the like are known.
Of the above two schemes, the JPEG scheme is suitable for compression of natural images such as photographs. The JBIG scheme is suitable for compression of binary images such as monochrome characters.
Since these image and audio data are digital data, high-definition, high-quality data copies can be easily generated.
In order to protect a copyrights on multimedia data, therefore, copyright information is embedded as digital watermark information in image and audio data.
The copyright information can be obtained by extracting the above digital watermark information from the multimedia data. This allows tracking of an unauthorized copy. As methods of embedding the above digital watermark information in image and audio data, for example, the scheme proposed by National Defence Academy, which uses the discrete Fourier transform, (Onishi, Oka, and Matsui, xe2x80x9cWater-mark Signature on Image with PN Sequencesxe2x80x9d, SCISxe2x80x2 9726B, January 1997) and the scheme proposed by Mitsubishi Electric Corp. and Kyushu University, which uses the discrete wavelet transform, (Ishizuka, Sakai, and Sakurai, xe2x80x9cExperimental Study on Security and Reliability of Digital Watermarking Technique Using Wavelet Transformxe2x80x9d, SCISxe2x80x2 97-26D, January 1997) are known in addition to the scheme proposed by NTT, which uses the discrete cosine transform, (Nakamura, Ogawa, and Takahashi, xe2x80x9cElectronic Watermarking Scheme in Frequency Domain for Protection of Copyright on Digital Imagexe2x80x9d, SCISxe2x80x2 97-26A, January 1997).
Conventionally, compression processing for image and audio data and digital watermark information embedding processing are independently performed. For example, digital watermark information is embedded in original data first, and then compression processing is performed upon completion of the embedding processing. For this reason, means for executing the respective processes are independently prepared. The overall size of the apparatus having these two means becomes inevitably large.
The present invention has been made to solve the above problems, and has as its principal object to efficiently embed digital watermark information in image or audio data.
More specifically, it is an object of the present invention to efficiently arrange both an image or audio data compression processing unit and an digital watermark information embedding unit in one apparatus.
In order to achieve the above objects, according to a preferred embodiment of the present invention, there is provided a data processing apparatus comprising input means for inputting digital data including at least one of image data and audio data, transforming means for transforming a data format of the digital data, compression means for compressing the digital data whose data format has been transformed by the transforming means, and embedding means for embedding digital watermark information in the digital data whose data format has been transformed by the transforming means, wherein the apparatus includes a plurality of image processing modes, compresses the digital data by using the transforming means and the compression means in a first mode, and embeds digital watermark information in the digital data by using the transforming means and the embedding means in a second mode.
It is another object of the present invention to embed digital watermark information in image data by an optimal method in accordance with the type of image data.
In order to achieve the above object, according to a preferred embodiment of the present invention, in the apparatus, the compression means includes quantization means for quantizing the digital data whose data format has been transformed by the transforming means and entropy coding means for performing entropy coding of the quantized data.
It is still another object of the present invention to properly set the sequence of compression of image or audio data and embedding of digital watermark information in the data.
In order to achieve the above object, according to a preferred embodiment of the present invention, in the apparatus, the compression means includes quantization means for quantizing the digital data whose data format has been transformed by the transforming means, and entropy coding means for performing entropy coding of the quantized data.
The above and other objects, features, and advantages of the present invention will be apparent from the following detailed description in conjunction with the accompanying drawings and the appended claims.